What causes smell disorders?

Smell disorders have many causes, some clearer than others. Most people who develop a smell disorder have recently experienced an illness or an injury. Common triggers are upper respiratory infections and head injuries.
In some patients, the exact cause for decreased smell remains unknown, even
after more serious causes are ruled out.

Among other causes of smell disorders are polyps in the nasal cavities, sinus infections, hormonal disturbances, or dental problems. Exposure to certain chemicals, such as insecticides and solvents, and some medicines have also been associated with smell disorders. People with head and neck cancers who receive radiation treatment are also among those who experience problems with their sense of smell.

How are smell disorders diagnosed?

Doctors and scientists have developed tests to determine the extent and nature of a person's smell disorder. Tests are designed to measure the smallest amount of odor patients can detect as well as their accuracy in identifying different smells. In fact, an easily administered "scratch and sniff" test allows a person to scratch pieces of paper treated to release different odors, sniff them, and try to identify each odor from a list of possibilities. In this way, doctors can easily determine whether patients have hyposmia, anosmia, or another kind of smell disorder.

Are smell disorders serious?

Yes. Like all of our senses, our sense of smell plays an important part in our lives. The sense of smell often serves as a first warning signal.
Smell can alert us to the smoke of a fire or the odor of a natural gas leak and dangerous fumes
or spoiled food. Perhaps more important is that our chemosenses are sometimes a signal of serious health problems. Obesity, diabetes, hypertension, malnutrition, Parkinson's disease, Alzheimer's disease, multiple sclerosis, and Korsakoff's psychosis are all accompanied or signaled by chemosensory problems like smell disorders.